This application claims the priority of Korean Patent Application No. 2002-63848, filed on Oct. 18, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method and apparatus for accurately measuring an amount of disc unbalance in a disc drive.
2. Description of the Related Art
Noise and vibration problems in a disc drive become more serious as the speed of the disc drive increases. Particularly, an unbalanced disc causes very serious noise and vibrations. The main cause of disc unbalance is an uneven distribution of mass around the disc due to thickness variations of the disc resulting from the molding process, offset of the center hole of the disc, or disc damage, etc. In order to remove or reduce the noise and vibrations in a disc drive, particularly, due to an unbalanced disc, the amount of disc unbalance should be measured.
A conventional method of measuring disc unbalance includes rotating the disc at a predetermined low speed; measuring a first eccentricity value of the disc after a spindle servo is stabilized at the predetermined low speed; rotating the disc at a predetermined high speed to maximize vibrations; measuring a second eccentricity value of the disc after the spindle servo is stabilized at the predetermined high speed; and detecting the amount of disc imbalance by calculating the absolute value of a difference between the first eccentricity value and the second eccentricity value. Since the speed of a disc drive varies with the amount of disc unbalance and the eccentricity value of the disc varies with the speed of the disc drive, the amount of disc unbalance is detected using the eccentricity values of the disc.
However, in the conventional method described above, the amount of disc unbalance may be measured differently according to an assembly condition of a disc drive. That is, when a disc drive is rigidly assembled, vibrations of the disc drive are more effectively suppressed and, accordingly, the eccentricity of a disc measured at that time is smaller than that measured when the disc drive is loosely assembled.
The present invention provides a method and apparatus accurately measuring an amount of disc unbalance regardless of an assembly condition of a disc drive.
The present invention also provides a method and apparatus measuring the amount of disc unbalance based on a time to reach a target RPM (Rotation Per Minute).
According to an aspect of the present invention, a method of measuring disc unbalance includes storing a plurality of reference disc unbalance values; measuring an RPM (Rotation Per Minute) of the disc; comparing the measured RPM with a target RPM; and when the measured RPM reaches the target RPM, detecting a reference disc unbalance value among the plurality of reference disc unbalance values based on an elapsed time to reach the target RPM.
According to another aspect of the present invention, a method of measuring disc unbalance includes measuring an RPM (Rotation Per Minute) of the disc when the disc is controlled to change its rotation speed from a predetermined low speed to a predetermined high speed; comparing the measured RPM with a target RPM; and when the measured RPM reaches the target RPM, detecting the amount of disc imbalance amount based on a time elapsed during the time that the rotation speed of the disc is changed from the predetermined low speed to the predetermined high speed to the time when the target RPM has been reached.
According to still another aspect of the present invention, the method further includes storing a plurality of reference disc unbalance values, and the amount of disc unbalance is found by detecting a reference disc unbalance among the plurality of reference disc unbalance values based on the elapsed time.
Further, in the method according to another aspect of the present invention, the measurement of the RPM of the disc may be performed regardless of a stabilized condition of a spindle servo of the disc drive.
According to another aspect of the present invention, an apparatus measuring disc unbalance includes a spindle motor rotating the disc; a first memory storing a target RPM (Rotation Per Minute); a second memory storing a plurality of reference disc unbalance values based on a time to reach the target RPM; and a system controller measuring a time to reach the target RPM after the spindle motor begins rotating and detecting a reference disc unbalance value from the second memory based on the measured time.
According to still another aspect of the present invention, an apparatus measuring disc unbalance includes a spindle motor rotating the disc; a motor driving unit driving the spindle motor; a first memory storing a target RPM (Rotation Per Minute); a second memory storing a plurality of reference disc unbalance values based on the time to reach the target RPM; and a system controller measuring an RPM of the spindle motor when the spindle motor is controlled to change from a predetermined low speed mode to a predetermined high speed mode and detecting, from the second memory, a reference disc unbalance value corresponding to the time elapsed to reach the target RPM after the spindle motor is controlled to change from the predetermined low speed mode to the predetermined high speed mode.
The system controller may measure the RPM in the predetermined high speed mode regardless of a stabilized condition of a spindle motor of the disc drive.
Further, the system controller may drive a timer to measure the elapsed time when the spindle motor is controlled to change from the predetermined low speed mode to the predetermined high speed mode.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.